Smacna Hangers and Supports

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CHAPTER 4

HANGERS AND SUPPORTS



CHAPTER 4

4.1 HANGING AND SUPPORTING

SYSTEMS

4.1.1 S4.0 Requirements

S4.1 Rigid round, rectangular, and flat oval metal

ducts shall be installed with support systems indicatedin Tables 4-1 to 4-3 and Figures 4-1 to 4-8. They shall

be installed as required to maintain alignment.

Horizontal ducts shall have a support within two feet

(0.61 m) of each elbow and within four feet of each

branch intersection. (Upper attachments to structures

shall have an allowable load not more than one-fourth

of the failure (proof test) load but are not limited to the

specific methods shown here.

4.2 COMMENTARY

The duct hanging system iscomposed of three elements,

the upper attachment to the building, the hanger itself,and the lower attachment to the duct. The manufacturer's

load ratings and application data should be followed for

all devices and materials.

4.2.1 Concrete Inserts

Concrete inserts must be installed before the concrete is

poured. They are used primarily where the duct layout

is simple and there is enough lead time to determine

accurate placement. The simplest insert is a piece of

bent flat bar. Manufactured inserts are available

individually or in long lengths; the latter are generally

used where many hangers will be installed in a smallarea, or where individual inserts cannot be precisely

spotted at the time of placing the concrete.

4.2.2 Concrete Fasteners

Concrete fasteners are installed after the concrete has

been poured and the forms have been removed. Their

application allows greater flexibility than concrete inserts

because their exact location can be determined after all

interferences between the various trades' work have

been coordinated.

There are several variations of powder-actuatedfasteners, which are placed by an explosive charge. These

fasteners should not be used in certain lightweight

aggregate concretes, or in slabs less than 4 inches (107

mm) thick.

HANGERS AND SUPPORTS

Expanding concrete anchors should be made of steel.

Nonferrous anchors tend to creep with vibration. Holes

for expanding fasteners are drilled either by a carbide

bit or by teeth on the fastener itself. The expansion

shield is "set" by driving it into the hole and expanding

it with the conical plug. The expansion nail is a lighter

duty fastener. Powder-actuated fasteners are popularfor smaller ducts.

4.2.3 Structural Steel Fasteners

Several types ofbeam clamps are available. Some should

be used with a retaining clip. Powder-actuated fasteners

may also be used on steel. Welded studs may be installed

using special welding equipment. Certain manufactured

devices that are driven onto the flange will support either

a rod or a band type hanger.

4.2.4 Cellular Metal Deck

Many office buildings are now built with a cellular steel

deck that carries the electrical and communication

systems and is covered with concrete fil l. The wiring in

the cells and the concrete above the deck preclude the

use of fasteners, such as sheet metal screws, that must

pierce the deck. Some manufacturers of this type of

deck now offer an integral hanging system. In cases

where there are no integral hangers at the required

hanging points, install the rod or strap hangers before

concrete placement, or install welded studsafterconcrete

placement. In all cases, the upper attachments to the

decking should be in place before the application of

fireproofing materials.

4.2.5 Upper Attachment

Upper attachment methods should be selected with care.

A safety factor of 4 or 5 (based on ultimate failure) is

practical unless it can be shown that few unpredictable

variables exist and that quality control is disciplined.

4.2.6 Hangers

Hangers are usually strips of galvanized steel or round

steel rod. For hangers made of round steel rod, use

uncoated hot-rolled steel except where the installationis in a corrosive atmosphere. Where corrosion is a

problem, hanger rods should be electro-galvanized, all-

thread rods or hot-dipped galvanized rods with their

threads painted after installation.

• HVAC Duct Construction Standards Metaland Flexible - Second Edition 4.1



4.2.7 Lower Attachment

The lower attachment is the connection between the

hanger and the duct section. Fasteners that penetrate

the duct may be sheet metal screws, blind rivets, or

self-tapping metal screws.

4.2.8 Hanger Spacing

A straight duct section is actually a box section beam

of considerable strength. As in many structures, the

joint is the weakest point, so that is where the support

is. Duct joints, however, are normally strong enough

to permit maximum hanger spacing at 8 (2.44) or 10

foot (3.05 m) intervals, even with one or two

intermediate joints. Very wide ducts require closer

hanger spacing in order to limit individual hangerloads

to safe values. They also require intermediate hangers

to prevent the upper portion of the duct from sagging.

4.2.9 Trapeze Selection

Trapeze members must be selected with careful attention

to the position of the loads on the horizontal bar. Load

analysis is discussed in the notes for Figures 4-4 and

4-5.

4.2.10 Riser Supports

Rectangular risers should be supported by angles or

channels secured to the sides of the duct with welds,

bolts, sheet metal screws, or blind rivets. Here again,

for ducts over 30 inches (762 mm) wide, caution must

be used in fastening the support tothe sheet because the

expansion of the sheet due to internal pressures will

tend to tear the fasteners out. Riser support intervals

should be at one or two story intervals, i.e., 12 feet

(3.66 m) to 24 feet (7.32 m), as suitable for loading.

Another method isto support the riser by its reinforcing.

The load can be transferred to the riser support by angles

or by rods.

4.2.11 Hanging System Selection

The selection of a hanging system should not be taken

lightly not only because it involves a significant portion

of the erection labor, but also because an inadequate

hanging system can be disastrous. In any multiple

hanger system, the failure of one hanger transfers thatits load to adjacent hangers. If one of these fails, an

even greater load is transferred to the next. The result

is a cascading failure in which an entire run of duct

might fall.

There are many hanger alternatives, especially in the

upper attachments. Besides structural adequacy, the

contractor's choice of hanging system must also take

into account the particulars of the building structure,

the skills of the workmen, the availability of tooling,

and the recommendations ofthe fastener manufacturer.

Because of these variables, it is suggested that the

hanging system be the contractor's choice, subject tothe approval of the mechanical engineer.

Figures in this manual show typical hanger

constructions. When special conditions require high

safety factors or the ability to withstand vibrations,

individual concrete or steel attachments can be specified

to be capable of supporting test loads equal to the

minimum rating listed when they are tested in

accordance with methods described by Underwriters'

Laboratory, Inc., for Pipe Hanger Equipment, Bulletin

UL 203, latest edition. See pages 3-19 to 3-21 for

support of flexible duct.

The supports discussed here are not seismicly qualified.

Refer to SMACNA's Seismic Restraint Manual for

additional reinforcement required by earthquake

hazards.

4.2HVAC DuctConstruction Standards Metal and Flexible - Second Edition •



ALPHABET LETTER ONLY INDICATES AN ALTERNAllVE LOCAllON OR SITUAllON

THAT MAY BE PERMITTED OR RESTRICTED BY DESIGN DOCUMENTS. ILLUSTRATIONS

OF CONCRETE AND STEEL DO NOT PRECLUDE ATTACHMENTS TO WOOD.

STRUCTURES

FILL

': ~ _ '~.'.~ .~

~. .'

" ' ' ' :BCD

PRECAST JOIST

A

CONCRETE SLAB

R* IS A BRIDGE MEMBER

~ L M~

. . . . . ..

oN

METAL DECK

STEEL BEAMS

METAL DECK(CELLULAR)

SECllON A-A

OPEN WEB JOIST

ALTERNATE LOCATION

IS ON TOP OF JOIST CHOR

CONVENllONAL HANGER METHODS AND DEVICES

CONCRETE INSERTS, SINGLE

CONCRETE INSERTS, SLOTTEDPOWDER ACTUATED FASTENERS·C· CLAMPS

WELDED STUDS

FRICllON CLAMPS

STRAP

ROD, THREADED, UNTHREADED

BRIDGEBEAM CLAMP, HALF FLANGE

BEAM CLAMP, FULL FLANGE

EYE BOLT (OR ROD)TOGGLE BOLTS

DRILLED HOLE AND BOLTSTANCHION

SELF TAPPING SCREWS PLUS STRAPSDROP IN EXPANSION ANCHORS

KNEE BRACKET FROM WALL

LAG SCREW EXPANSION ANCHORNAILED PIN FASTENERS

RIVETS

SWAY BRACING"FISH" PLATE OR WASHER AND RODHOOK OR LOOP

VlBRAllON ISOLATORWIRE

SELECT HANGERS FOR TYPE OF STRUCTURE AND SUSPENSION.DO NOT EXCEED ALLOWABLE OR SPECIFIED LOAD LIMITS.

ALLOWABLE LOAD ON UPPER ATTACHMENT IS 1/4 OF FAILURE LOAD

HANGER ATTACHMENTS TO STRUCTURES FIG. 4-1

HVAC Duct Construction Standards Metal and Flexible - Second Edition 4.3



UNLESS OTHERWISE APPROVED ALLOWABLE LOAD ON UPPER ATTACHMENT IS 1/4 OF FAILURE LOAD.UPPER ATTACHMENTS MAY BE TO WOOD STRUCTURES ALSO.

2

FLAT BAR CONCRETE INSERT

MANUFACTURED

CONCRETE INSERTS

, "J:" ..i : ...... . . ....

t • ". ..'

. . . . . . .. ; / : . ~ . " ~ . ~ : ..: ...•...'. ~.~:. '-~. .

~, .:.. , ;0"., ,

• E3D---~~~~~~~STRAP

WASHERNUT

, '

':, • ,.', '. rI,,' ,

4*

RETAINING CLIPHANGER ROD

6a C-CLAMP wi RETAINING CLIP OR

6b C-CLAMP W I LOCK NUT (OPTIONAL)

A HANGER STRAP MAY ALSO BE C

CLAMPED TO THE STRUCTURAL FLANGE

WASHER MAY BE OMITTED WITH100 LB (45 KG) MAX LOAD ON

22 GA (0.85 mm) STRAP WHEN

FOLDED

HANGERSTRAP

HANGERROD

10*

EXPANSION SHIELDS EXPANSION NAIL

CONCRETE ANCHORS

POWER ACTUATED

STUDS INTO STEEL

(STRUCTURE OR DECK)

WIRE USE IS NOT

PRECLUDED BY THESE

ILLUSTRATIONS.

WELD OR

DOUBLE

NUT

ALTERNATENUT &

BOLTOUPLING

HANGER RODNUT

"""___HANGER STRAP _ _,.. BEARING PLATE

1512 13'"

WELDED STUDS

'" IMPORTANTI PREVENT BENDING OFSTRAP AT 90' BEND UNDER LOAD.

FRICTION CLAMPS

THE NUMBERS ASSOCIATED WITH THE ART ARE

ONLY FOR CONVENIENT REFERENCE.

UPPER ATT ACHMENT DEVICES - TYPICAL FIG. 4-2

4 . 4 HVAC Duct Construction Standards Metal and Flexible - Second Edition •



UNLESS O TH ERW ISE A PPRO VED A LLOWA BLE LO AD O N UPPER A TTA CHM ENT IS 1/4 O F FA ILURE LO AD.

WIRESOLE IN DECK

CONCRETEFILL

1 "6

H-ANGER STRAP1· (25 mm)M IN. DIA . CO IL

BOLT, PIN ORSCREW PENETRAT ION

SYSTEM ATTACHMENTSMUS T N OT D EFLE CTUNDER LOAD .

19CUp----T-~~------~~

20 BENT STRAP -- .. .. ._O R LOOP EDWIRE

H AN GE R R OD

21

WELDED STUDW IT H NUT

PRE VENT B ENDING OFSTRAP AT THE 90· BEND.

H ANGER STRAP

AVOID PENETRAT ION OF ELECTRIC A L ENCLOSURES

UPPER ATTACHMENTS - TYPICAL FIG. 4-3

• HVAC Duct Construction Standards Metal and Flexible - Second Edition 4.5



TABLE 4-1

RECTANGULAR DUCT HANGERS

MINIMUM SIZE

MAXIMUM Pair at 10ft Spacing Pair at 8 ft Spacing Pair at 5 ft Spacing Pair at 4 ft SpacingHALF OF

DUCT WIREI WIREI WIREI WIREIPERIMETER STRAP ROD STRAP ROD STRAP ROD STRAP ROD

PI2 = 30" 1" x 22 gao10 gao

1"x22ga.10 gao

1" x 22 ga.12 ga.

1"x22ga.12 gao

(.135") (.135") (.106") (.106")

PI2 = 72" 1"x18ga. 3/8" 1"x20ga. 1/4" 1" x 22 ga. 1/4" 1"x22ga. 1/4"

PI2 = 96" 1"x16ga. 3/8" 1"x 18ga. 3/8" 1"x20ga. 3/8" 1" x 22 gao 1/4"

P/ 2 = 120" 1 112" x 16 gao 1/2" 1"x16ga. 3/8" 1"x 18ga. 3/8" 1" x 20 ga. 1/4"

PI2 = 168" 1 1/2" x 16 gao 1/2" 1 1/2" x 16 gao 1/2" 1"x 16ga. 3/8" 1" x 18 gao 3/8"

PI2 = 192" Not Given 112" 1 1/2" x 16 ga" 112" 1"x 16ga. 3/8" 1"x 16ga. 3/8"

PI2 = 193" up SPECIAL ANALYSIS REQUIRED

WHEN STRAPS ARE LAP JOINEDSINGLE HANGER MAXIMUM ALLOWABLE LOAD

USE THESE MINUMUM FASTENERS:

STRAP WIRE OR ROD (Dia.)

1" x 18, 20, 22 gao - two #10 or one 1/4" bolt 1" x 22 ga.- 260 Ibs. 0.106"- 80 Ibs.

1" x 16 gao- two 1/4" dia. 1" x 20 ga.- 320 Ibs. 0.135"- 120 Ibs"

1 1/2" x 16 gao -two 3/8" dia" 1" x 18 ga.- 420 Ibs. 0.162"- 160 Ibs.

Place fasteners in series, not side by side. 1" x 16 ga.- 700 Ibs. 114"- 270 Ibs.

1 1/2" x 16 ga.- 1100 Ibs. 3/8"- 680 Ibs.

112"- 1250 Ibs.

5/8"- 2000 Ibs.

3/4"- 3000 Ibs.

NOTES:

1. Dimensions other than gage are in inches.

2. Tables allow for duct weight, 1 Ib./sf insulation weight and normal reinforcement and trapeze weight,

but no external loads!

3. For custom design of hangers, designers may consult SMACNA's Rectangular Industrial Duct

Standards, the AISI Cold Formed Steel Design Manual and the AISC Steel Construction Manual.

4. Straps are galvanized steel; other materials are uncoated steel.

5. Allowable loads for P /2 assume that ducts are 16 gao maximum, except that when maximum duct

dimension (w) is over 60" then p/2 maximum is 1.25 W.

6. For upper attachments see Fig. 4-2.

7. For lower attachments see Fig. 4-4.8. For trapeze sizes see Table 4-3 and Fig. 4-5.

9. 12, 10, or 8 gaowire is steel of black annealed, bright basic, or galvanized type.

4 . 6 HVAC Duct Construction Standards Metal and Flexible - Second Edition •



TABLE 4-1M

RECTANGULAR DUCT HANGERS

MINIMUM SIZE

MAXIMUM Pair at 3 m Spacing Pair at 2.4 m Spacing Pair at 1.5 m Spacing Pair at 1.2 m SpacingHALF OF

DUCT WIRE! WIREI WIRE! WIREIPERIMETER STRAP ROD STRAP ROD STRAP ROD STRAP ROD

PI2 = 760 25.4 x 0.85 3.4 25.4 x 0.85 3.4 25.4 x 0.85 2.7 25.4 x 0.85 2.7

PI2 = 1830 25.4 x 1.31 9.5 25.4 x 1.00 6.4 25.4 x 0.85 6.4 25.4 x 0.85 6.4

P /2 = 2440 25.4 x 1.61 9.5 25.4 x 1.31 9.5 25.4 x 1.00 9.5 25.4 x 0.85 6.4

P/ 2 = 3050 38.1 x 1.61 12.7 25.4 x 1.61 9.5 25.4 x 1.31 9.5 25.4 x 1.00 6.4

PI2 = 4270 38.1 x 1.61 12.7 38.1 x 1.61 12.7 25.4 x 1.61 9.5 25.4 x 1.31 9.5

PI2 =4880 Not Given 12.7 38.1 x 1.61 12.7 25.4 x 1.61 9.5 25.4 x 1.61 9.5

PI2 = More SPECIAL ANALYSIS REQUIRED

WHEN STRAPS ARE LAP JOINEDSINGLE HANGER MAXIMUM ALLOWABLE LOAD

USE THESE MINUMUM FASTENERS:

STRAP WIRE OR ROD (Dia.)

25.4 x 1.31,1.00,0.85 mm - one 6.4 boll 25.4 x 0.85 -118 Kg 2.7 -36 Kg

25.4 x 1.61 mm - two 6.4 bolts 25.4 x 1.00 -145 Kg 3.4 - 54 Kg

38.1 x 1.61 mm - two 9.5 bolts 25.4 x 1.31 -191 Kg 4.1-73 Kg

Two boils must be in series, not side by side. 25.4 x 1.61 - 318 Kg 6.4-122 Kg

38.1 x 1.61 - 500 Kg 9.5- 308 Kg

12.7 - 567 Kg

15.9 - 907 Kg

19.1 - 1360 Kg

NOTES:

1. Dimensions other than hanger spacings are in millimeters.

2. Tables allow for duct weight, 4.89 Kg/m2 insulation weight and normal reinforcement and trapeze

weight, but no external loads!

3. For custom design of hangers, designers may consult SMACNA's Rectangular Industrial Duct

Standards, the AISI Cold Formed Steel Design Manual and the AISC Steel Construction Manual.

4. Straps are galvanized steel; other materials are uncoated steel.

5. Allowable loads for P /2 assume that ducts are 1.61 mm maximum, except that when maximum duct

dimension (w) is over 1520 mm then p/2 maximum is 1.25 w.

6. For upper attachments see Fig. 4-2.

7. For lower attachments see Fig. 4-4.

8. For trapeze sizes see Table 4-3 and Fig. 4-5.

9. 2.7, 3.4, and 4.1 mm wire is steel of black annealed, bright basic, or galvanized type.

HVAC Duct Construction Standards Metal and Flexible - Second Edition 4.7



TABLE 4-2

MINIMUM HANGER SIZES FOR ROUND DUCT

Maximum Wire

Dia. Spacing Dia. Rod Strap

10" dn 12' One 12ga. 1/4" 1"x 22gao250mmdn 3.7m One 2.75 mm 6.4mm 25.4 x 0.S5mm

11-1S" 12' Two 12ga. 1/4" 1"x 22gao

or One Sga.

460mm 3.7m One4.27mm 6.4mm 25.4 x 0.S5mm

19-24" 12' Two 10ga. 1/4" 1"x 22gao

610mm 3.7m Two 3.51 mm 6.4mm 25.4 x 0.S5mm

25-36" 12' TwoSga. 3/S" 1"x20ga.

900mm 3.7m Two2.7mm 9.5mm 25.4 x 1.00 mm

37-50" 12' Two 3/S" Two 1" x 20 gao

1270mm 3.7m Two9.5mm (2) 25.4 x 1.00mm

51-60" 12' Two 3IS" Two 1" x 1Sgao

1520mm 3.7m Two9.5mm (2) 25.4 x 1.31 mm

61-84" 12' Two 3/S" Two 1" x 16gao

2130mm 3.7m Two9.5mm (2) 25.4 x 1.61 mm

NOTES:

1. Straps are galvanized steel; rods are uncoated or galvanized steel; wire is black annealed, bright

basic, or galvanized steel. All are alternatives.

2. See Fig. 4-4 for lower supports.

3. See Figs. 4-2 and 4-3 for upper attachments.

4. Table allows for conventional wall thickness, and joint systems plus one Iblsf (4.89 Kg/m2) insulation

weight. If heavier ducts are to be installed, adjust hanger sizes to be within their load limits; see

allowable loads with Table 4-1. Hanger spacing may be adjusted by special analysis.

5. Designers: For industrial grade supports, including saddles, single load trapeze loads, longer spans

and flange joint loads, see SMACNA's Round Industrial Duct Construction Standards.

6. See Figs. 3-9 and 3-10 for flexible duct supports.

4.8 HVAC Duct Construction Standards Metal and Flexible· Second Edition _



STRAP HANGERS

SCREWS - - - ~ - - - - J - LSCREWS MAY BE 1" MIN.

OMITTED IF HANGER LOOPS (25 mm)

LOAD RATED

FASTENERS

36" (914 mm)DIA.MAX.

HANGERS MUST NOT DEFORM DUCT SHAPE

HANGER RODS, WIRES

OR

STRAPS

BAND

ONE HALF-ROUND MAY BE USED

IF DUCT SHAPE IS MAINTAINED.

TRAPEZE HANGERS

STRAP OR

ANGLE ROD

UNLESS FOOT

OF STRAP

IS PLACED

UNDER A

BOTTOM

REINFORCEMENT

24" (610 mm)

DIA.MAX.

ALTERNATE

LOCATION (VERIFY UPPER

TRAPEZE lOAD

CAPACITY)

REINFORCEMENT MAY BE USED FOR ATTACHMENT

IF IT QUALIFIES FOR BOTH DUTIES.

DO NOT EXCEED AllOWABLE LOAD LIMITS.

LOWER HANGER ATTACHMENTS FIG. 4-4

., HVACDuct Construction Standards Metal and Flexible - Second Edition 4.9



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4.10 HVAC Duct Construction Standards Metal and Flexible - Second Edition .,



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• HVAC Duct Construction Standards Metal and Flexible - Second Edition 4011



r - - -W-I

lOAD DIAGRAM TRAPEZE SUPPORT

a

I - - - - -l~~1

4.12 HVAC Duct Construction Standards Metal and Flexible - Second Edition

ra---- ~-

W

2-- a

--_ ------DEFlECTIO~ : = . . _ s -

~-------l---------

P

2

P

2

W = Duct Width, inchesl Distance between supports on the trapeze, inches (mm)

Distance between support and duct side, inches (mm)

Deflection, inches, suggested maximum 3 /S" (9.5 mm) 6

Modulus of elasticity 129,000,000 psi for steel) (200 x 10 kPa)

Moment of Inertia, in.4 (mm 4 )

Section Modulus, in.3 (mm 3)

P Weight of duct, reinforcements, insulation, etc.-not to exceed allowable load for

stress or def lect ion l imits

P1 =Weight of duct material of an area W x W in ft2 (m2) times 2.6561b/ft2 (127 newtons/m2)

M Moment, in.-Ib. (mN x m)

S Allowable stress, steel = 15,000 psi (103,425 KPa) for bending stress.

Shear stress alone should not exceed 7,500 psi . (51,713 kPa)

F Shear load, Ibs. (kg)

A Cross sectional area, in~ (mm2)

aD

E

I

Z

BENDING STRESS

SA = 15,000 psi = ~Z

P=2SZ

_ P1(_b_ -1) = 30000."£ - P1(_b_ -1)a 2a 'a 2a

DEFLECTION

(P - P t ) a (3l2 - 4a2)D = - -- -- -- - - -- -- -- -

2 (24EI)+

Consul t re ference texts for other conditions of loading. For round duct loads on

trapeze angles see the Round Industr ial Duct Construct ion Standards

SHEAR STRESS

S S = 7,500 Psi = ~P

2aP = 15000 A (maximum)

Notice: Formula constants here are not in metric uni ts.

TRAPEZE LOAD DIAGRAM

J ]

FIG. 4-5



TIE RODS LOCATED AT EQUAL

SUBDIVISIONS OF W

DUCT REINFORCEMENT

TIE REINF. (SEE FIG. 1-11

AND FIG. 1-12)

FLANGED JOINT

(OPTIONAL) i---ANGER OPTION

1

1

• HVACDuctConstructionStandardsMetal andFlexible· SecondEdition 4.13

TIE ROD OPTION

HANGER COUPLED TO ~EXISTING TIE ROD

(OPTIONAL) rV

HANGER

T 1-------- L2--------<-

1 1 71 HGR .........

HANGER --.I i HGR ~I--.---- L 1------1

HANGER AIT ACHED TO TRAPEZE BAR

L1 + 0 OR L 2 + D DEFINES P /2 FOR TABLE 4-1

LARGE DUCT SUPPORT FIG. 4-6



RISER SUPPORTS • FROM FLOOR FIG. 4·7

.-,ft----..;.._ HANGER ROD BETWEENRISER SUPPORT B eRISER REINFORCING

'-- __ RISER REINFORCING

(FOR DUAL DUlY)

FIG. B

...MINIMUM NUMBER OF FASTENERS

ON EACH OF TWO SUPPORT BARS

LARGEST DUCT DIM.

lS" and down

17" - 24"

over 24·

MINIMUM NUMBEROF FASTENERS

23

Largest duct dim.

Divided by 8

Locate a fastener within 2" of the duct edges. Locate others at evenlyspaced intervals. See Table 4-4 on page 4.1S.

SUGGESTED SIZING FOR

SUPPORT OF 12 FT. OF DUCT

DUCT SIZE ANGLE

36· x 18" 1/2" x 1 1/2" x 1/8-

48" x 24- 1/2" x 1 1/2" x 1/8-

SO" x 30" 1/2" x 1 1/2" x 3/16"

60· x 60" 1/2" x 1 1/2" x 1/4·or 2" x 2" x l/S"

FIG. A

3" MAX. OVER 60" - INCREASE ANGLE SIZE AS

DISTANCE REQUIRED FOR SPACE B e DUCT SIZE

TO SUPPORT

SUPPORT RISERS SO THAT THEY ARE IN TENSION

4.14 HVAC Duct Construction Standards Metal and Flexible - Second Edition •



I Ir-----------------1l ~-_-----_- .....--J

I I I I I I ALTERNATIVE SUPPORT

I I I I ,-r--- TO RISER REINFORCEMENT

I I ABOVE FLOOR

...-1+------ HANGER ROD BETWEEN

RISER SUPPORT &

RISER REINFORCING

'-- __ RISER REINFORCING

(FOR DUAL DUTy)

MINIMUM NUMBER OF FASTENERS

ON EACH OF TWO SUPPORT BARS

MINIMUM NUMBER

OF FASTENERS

2

3

Largest duct dim.

Divided by 8

Locate a fastener within 51 mil } of the duct edges. Locate others at evenly

spaced intervals. See Table 4-4 on page 4-16.

LARGEST DUCT DIM.

406 mm and down

432 mm - 610 mm

over 610 mm

51 mm --DUCT SIZE ANGLE

SUGGESTED SIZING FOR

SUPPORT OF 3.7 M OF DUCT

ANGLE

OVER 1524 mm -INCREASE ANGLE SIZE

AS REQUIRED FOR SPACE & DUCT SIZE

914 x 457 mm 38.1 x 38.1 x 3.2 mm

1219 x 610 mm 38.1 x 38.1 x 3.2 mm

1524 x 762 mm 38.1 x 38.1 x 4.8 mm

1524 x 1524 mm 38.1 x 38.1 x 6.4 mm

or 51 x 51 x 3.2 mm.

7.62mm

MAX. DISTANCE

TO SUPPORTIG. A

RISER SUPPORTS - FROM FLOOR FIG.4-7M

• HVAC Duct Construction Standards Metal and Flexible· Second Edition 4.15



ANCHOR

FIG. A

-- - - - - - - SHOWS SUPPLEMENTAL

FASTENER LOCATIONS

FIG.B

FIG. A - SUGGESTED SIZING

DUCT SIZE BAND

1 1/2"x16 GA.

1"x1/S"

1S"x12"

24"x20"

TABLE 4-4

DUCT GAGE

ALLOWABLE

LOAD PER

FASTENER·

2S,26

24,22,20

1S.16

251b

351b

50Ib

• WELD. BOLT OR NO. S SCREW (MIN.)

DEVIATION PERMITTED BY OTHER

ANALYSIS. X=1", Y=2"; ADD OTHERS TO

ACCOMODATE LOAD. MINIMUM OF 3ON 24"WIDTH AND UP. ADD ALONG SIDES NEAREST

ANCHORS.

",,,--' . . . . ., ,I \

\I , II I I\ I I

\ , /, '"- . . . . _ - , , -

(HANGER)

SEE KNEE BRACKET TABLES

IN THE ROUND INDUSTRIAL STDS.

FIG. B - SUGGESTED SIZING

DUCT SIZE ANGLE

30" x 12"

36" x 1S"

42" x 24"

4S" x 30"

1"x1"x1/S"

l"x 1"x lIS"

1 1/4" xl 1/4" x 1/S"

1 1/4" x 1 114" x lIS"

NOTES: 1. BRACKETS ARE SIZED FOR 12 FEET OF DUCT. MAXIMUM.

2. LOCATE DUCTS AGAINST WALL OR MAXIMUM OF 2" AWAY FROM WALL.

3. EACH WALL ANCHOR SHALL SATISFY THE FOLLOWING CRITERIA UNLESS OTHER

ANALYSIS IS MADE:

A. TENSILE LOAD = 3/ S x DUCT WEIGHT; SAFETY FACTOR 4.

B. SHEAR LOAD x 1/ 2 x DUCT WEIGHT; SAFETY FACTOR 4.

SUPPORTS FROM WALL FIG. 4-8

4.16 HVAC Duct Construction Standards Metal and Flexible - Second Edition



FIG. A - SUGGESTED SIZING

DUCT SIZE

457 x 300 mm

610 x 508 mm

BAND

38.1 x 1.61 mm

25 x3.2 mm

TABLE 4-4

DUCT GAGE

ALLOWABLE

LOAD PER

FASTENER'

0.48, 0.58 mm 11.3 KG

0.70, 1.00 mm 16 KG

1.31.1.61mm 23 KG

• WELD, BOLT OR NO.8 SCREW (MIN.)

DEVIATION PERMITTED BY OTHER

ANALYSIS. X =2 5 mm, Y = 51 mm; ADD

OTHERS TO ACCOMODATE LOAD. MINIMUM

OF 3 ON 610 mm WIDTH AND UP. ADD

ALONG SIDES NEAREST ANCHORS.

ANCHOR

FIG. A

-------- SHOWS SUPPLEMENTAL

FASTENER LOCATIONS

.,--- . . . . ., ,/ \I \

I , II I I\ I I

\ ~ /

" , -'. . . . . ._-"

(HANGER)

SEE KNEE BRACKET TABLES

IN THE ROUND INDUSTRIAL STDS.

FIG. B - SUGGESTED SIZING

DUCT SIZE

762 x 305 mm

914 x 457 mm

1067 x 610 mm

1219 x 914 mm

ANGLE

25 x 25 x 3.2 mm

25 x 25 x 3.2 mm

31.8 x 31.8 x 3.2 mm

31.8 x 31.8 x 3.2 mm

FIG.B

NOTES: 1. BRACKETS ARE SIZED FOR 3.7 M OF DUCT, MAXIMUM.

2. LOCATE DUCTS AGAINST WALL OR MAXIMUM OF 51 mm AWAY FROM WALL.

3. EACH WALL ANCHOR SHALL SATISFY THE FOLLOWING CRITERIA UNLESS OTHER

ANALYSIS IS MADE:

A. TENSILE LOAD = 318 x DUCT WEIGHT; SAFETY FACTOR 4.

B. SHEAR LOAD x 112x DUCT WEIGHT; SAFETY FACTOR 4.

SUPPORTS FROM WALL FIG.4-SM

• HVAC Duct Construction Standards Metal and Flexible - Second Edition 4.17



o o

FASTENER·

o

o D

o oF========::f--DUCT JOINT-~~~~~~~~§Fr5

CONNECTION. 0

REFER TO '

FIG. 3-2

SPLIT BAND SUPPORTDIRECTLY ON FLOOR SLAB

SPLIT BAND SUPPORT BY SUPPLEMENTAL ANGLE ORCHANNEL SPANNING THE SLAB OPENING. USE AISCSTEEL HANDBOOK FORMULA FOR SIZING BEAMS WITH

TWO CONCENTRATED LOADS.

SUGGESTED SIZING FOR SPUT BAND SUPPORT

FOR 12 FT OF DUCT

BOLT DIA. BAND SIZE

1/4" 1" x 16 GA

(6.35 m m ) (25.4 m mx 1.61 m m )

1/4" 1 1/2" x 16 GA

(6.35 m m ) (38.1 m mx 1.61 m m )

~ ~ /8ftj\9.52 m m )

3/8"

(9.52 m m )

2· x 16 GA

(51 m m x1.61 m m )

2· x 10 GA

(51 m m x3.51 m m )

DUCT DIA.

UP TO 12" DIA 24 GA

(UP TO 305 m mDIA 0.70 m m )

13" TO 24" DIA 20 GA

(330 m m TO 610 m mDIA 1.00 m m )

25" TO 36" DIA 20 GA

(635 m m TO 914 m mDIA 1.00 m m )

37" TO 60" DIA 18 GA

(940 m m TO 1524 m mDIA 1.31 m m )

... MINIMUM OF TWO

FASTENERS IN EACH

HALF OF BAND.

OTHERWISE SPACETHEM AT 8· (200 m m )AND SO THAT THELOAD SATISFIES

TABLE 4-4 ON FIG. 4-8.

RISER SUPPORT • FROM FLOOR FIG. 4·9

4.18 HVAC Duct Construction Standards Metal and Flexible - Second Edition •



FOR TYPICAL ISOLATION DEVICES SEE APPENDIX A-32

FOR UPPER ATIACHMENT METHODS SEE FIGURES 4-2 AND 4-3

RECESS IN FLOORWASHER\ ; & N U T

rANGL

SADD

I

FINISHED FLOOR

I I

r ~ . ~ . I~ . r~. . .b ' • • •. . ~

I I I I

I

~ ~

I HANGER

I I ROD

I II I

E

I IE

7 AIR SUPPLY UNIT

F .E 1 =

II IV 'ijf'1

FIG. A

SUSPENSION METHODS SHOWN ARE SOME OF MANY

ALTERNATIVES THAT MAY BE ENGINEERED BY DESIGNERS.

ANGLE ANCHORED IN CONCRETE

CHAN

SADD

I \ I

+ . . \ ~ ' .. ~ 6 t > ' . , :~+. . . . .

~ . . t > 6 I>. . . .~ .. . .

I I "T - ItI "T T "T "T "T tt r-"T I IIII

~ ~

ANGLEI

HANGERII

I

IIIII

NEL I

LEI

7I AIR SUPPLY UNITI

[ II

" " I III II I

FIG. B

UNITUNIT UNIT

.-- PLATFORM OR TRAPEZE

HVAC UNIT SUSPENSION FIG. 4-10

Smacna Hangers and Supports

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